Atypical for a zoologist, I’m terrified of most animals. Growing up in the wildlife paradise of Stoke-on-Trent, my mother’s response was a fairly standard “they’re more scared of you than you are of them”. Maybe that’s not true of my childhood interactions with Canadian Geese - but new research published in the journal Science highlights widespread changes in the behaviour of mammals, which the authors attribute to fear of humans. We’re driving our fellow mammals into the night: increasing nocturnal activity in the presence of human activity, on average, by a factor of 1.361. This means, for example, that if a species naturally split its activity 50% day and 50% night, around humans the night time activity would increase to 68%.
What is it that we’re doing to push our Class-mates under the cover of darkness? The authors pulled together 76 studies, from across the globe, measuring activity patterns in relation to anthropogenic stressors including vehicles, agriculture, mining, hunting, building works, and even hiking. Significant increases to nocturnality were found in response to every single form of human presence that they tested. Surprisingly, the diel pattern shifts caused by non-lethal activities like hiking and other recreational activities were statistically indistinguishable from those caused by lethal activities such as hunting - which the authors say suggests “that animals perceive and respond to human threats even when they pose no direct risk”1.
These findings were consistent across habitats, continents, normal activity periods, diet types, and body size classes. Even apex predators like the lion (Panthera leo) and the black bear (Ursus americanus), which have recent evolutionary histories largely devoid of predation risk, appear to be responding to human activity by increased nocturnality.
These findings sound scary: humans, acting as a diurnal apex “super predator”, not content with constricting animal spatial distributions through massive habitat destruction and defaunation are also affecting their temporal distribution too.